The hallmark of most B-cell neoplasia is proliferation of B-cells and clonal rearrangement of the immunoglobulin gene, which is lambda or kappa light chain restricted. Since fresh tissue is not always available to determine clonality, immunohistochemical (IHC) staining for kappa and lambda light chains is often performed on formalin-fixed, paraffin-embedded (FFPE) tissue. Commercially available polyclonal antibodies typically produce high background staining and have a significant false negative rate, which makes it difficult to prove clonality. We developed a series of monoclonal antibodies to human kappa and lambda light chain constant regions by immunizing mice with purified kappa and lambda immunoglobulin light chains.